Internal combustion engines, in particular diesel and gasoline engines, are increasingly provided with turbocharger arrangements. The turbocharger arrangement serves for compressing the charge air fed to the internal combustion engine, with the result that an increase in power can be brought about. Conversely, a stipulated power can be achieved by a supercharged engine with a lower cubic capacity, as a result of which a smaller and lighter version and a drive having lower fuel consumption can be obtained. Turbochargers of this type are usually driven by the exhaust gas stream of the internal combustion engine, for which purpose the turbocharger arrangement has a turbine wheel which is arranged in the exhaust gas stream. The turbine wheel may drive via a common shaft a compressor unit which compresses the charge air of the engine. Both the turbine wheel and the compressor unit may adjoin the turbocharger housing on the outside, so that a compressor-side and a turbine wheel-side end of the turbocharger housing or of the inner space can be defined.
A sealing system may be provided in the turbocharger to seal a turbine shaft and lubricated components from the turbine and compressor wheels. However, during some operating conditions oil may leak from the lubricated components into the compressor and/or turbine sides of the turbocharger. Oil that escapes on the compressor-side end contaminates the charge air, thereby leading to undesirable effects during combustion. Some of these undesirable effects are, for example, what are known as “megaknocks” or incomplete combustion. The particle emissions consequently rise, and it therefore becomes difficult to fulfill emission regulations. If oil escapes on the turbine wheel side, it may settle on downstream particle filters and catalysts, with the result that the functioning capacity of these is restricted, this likewise having an adverse effect upon emissions. US 2010/0139270 discloses a sealing system configured to seal lubricated components from the compressor and turbine wheels. However, the disadvantages described above with regard to the sealing system may be experienced in the sealing system described in US 2010/0139270.
To address at least some of the disadvantages discussed above, a turbocharger arrangement in an internal combustion engine is provided. The turbocharger arrangement includes a turbocharger housing surrounding a sealed inner space and a shaft extending through the turbocharger housing. The turbocharger arrangement further includes a turbine wheel arranged on the shaft and driving a compressor unit, a bearing arrangement mounting the shaft in the turbocharger housing, an oil supply device lubricating the bearing arrangement, and a pressure changing unit in fluidic communication with the sealed inner space configured to adjust the pressure in the sealed inner space based on engine operating conditions.
In this way, the pressure in the inner space may be adjusted to reduce the pressure different between the inner space and the compressor and/or turbine sides in the turbocharger. As a result, the likelihood of oil leakage into the compressor and/or turbine wheels is reduced, thereby improving combustion operation and reducing emissions.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. Additionally, the above issues have been recognized by the inventors herein, and are not admitted to be known.